This invention relates generally to belt and pulley drive mechanisms, and more specifically to an improved means whereby the tension of the belt can be adjusted.
Belt and pulley drive mechanisms have long been used in coupling a driving shaft such as that of an electric motor or other prime mover to a driven shaft such as that of a generator, fan or pump. In each of these applications, the driving and driven shafts are normally journaled for rotation by means of bearings or bushings. Proper tension must be maintained in the belt coupling the drive pulley to the driven pulley so that the belt will not slip, yet the tension must not be too great or the bearing/bushing life will be markedly reduced. Thus, a need exists whereby the tension of a V-belt or other flexible endless belt can be readily adjusted.
For exemplary purposes only and with no limitation intended, the present invention will be discussed in connection with its use in driving a centrifugal pump. It is to be understood, however, that the same approach may be used in a variety of other applications.
In U.S. Pat. No. 3,863,517 to Pareja entitled "Centrifugal Pump Mount" which is assigned to the assignee of the instant invention, there is described a belt tensioning arrangement in which the drive pulley is arranged to be driven by the power takeoff of an agricultural tractor while the driven pulley is coupled to the shaft of a centrifugal pump. In this arrangement, the drive pulley has a first bore extending inward on one side of its hub for receiving a motor's output shaft and a second or counterbore extending inward from the opposite side of its hub for receiving thrust bearings which are used to journal the drive pulley to a first end of a stub shaft. A bracket is bolted to the pump has a bore therein for receiving the other end of the stub shaft. The two ends of the stub shaft are offset by a predetermined eccentricity. Means are provided for adjusting the radial position of the stub shaft within the bore in the bracket. As the stub shaft is rotated in one direction or the other, the amount of eccentricity adds to or subtracts from the nominal distance between the driving shaft and the shaft of the driven centrifugal pump.
The present invention is deemed to be an improvement over the prior art as represented by the aforereferenced U.S. Pat. No. 3,863,517. While the arrangement disclosed in that eariler patent is entirely workable and capable of achieving the objects and advantages set forth in that patent, when compared to the present invention, it proves to be relatively more costly to manufacture and slightly more difficult to repair and maintain. For example, the tensioning arrangement shown in the eariler Pareja '517 patent requires an eccentric stub shaft which is relatively expensive to make. Also, rather than a conventional pulley, the eariler device requires that the pulley have a counterbore for accommodating thrust bearings for supporting the stub shaft. The locking mechanism for the belt tensioning lever including the slotted cup housing and associated adjustable locking lever also result in a more costly approach. The belt tensioning approach set forth in the resent specifically offers a number of advantages over prior art other than that represented by the Pareja '517 patent. For example, many of the centrifugal pumps in use today require that the power takeoff (PTO) drive attachment be disassembled in order to remove the pump for servicing. With the mounting and belt tensioning arrangement of the present invention, however, by removing only a single bolt, the pump can be separated from the PTO drive hookup. It is found that the tensioning arrangement of the present invention provides a high resistance to slip with less bearing load and with little or no chatter or vibration. Furthermore, the design of the present invention tends to be lighter, more compact without sacrifice in the effective life of the assembly and its component parts.
It is accordingly a principal object of the present invention to provide a new and improved arrangement for adjusting and holding the tension of an endless belt in a belt and pulley drive system.
Another object of the invention is to provide an improved belt tensioning arrangement which offers the advantages of lower manufacturing cost, simplicity of adjustment, high reliability and greater ease of repair and maintenance than heretofore obtainable using prior art techniques.